It’s not uncommon for researchers to find chemicals from personal care products and pharmaceuticals in waterways. Synthetic hormones, antibiotics, and recreational drugs that aren’t metabolized by the body can become water pollutants once they’ve been flushed down the drain. Because sewage treatment plants aren’t designed to remove these compounds, they can end up in rivers, lakes, and streams.

Increasingly, researchers have identified another source of these trace pollutants, commonly known as micropollutants. In addition to . . .